Researchers use a magnetic field to trigger, pinpoint epileptic seizures

May 28, 1993|By Douglas Birch | Douglas Birch,Staff Writer

A team of researchers from the United States and Switzerland reported Wednesday that they have been able to trigger seizures in two epilepsy patients by exposing the patients' heads to a weak magnetic field.

Team members, speaking at the American Geophysical Union meeting in Baltimore, say they will try to determine whether these fields switch on seizures by twisting, pushing or pulling fine particles of magnetite, a highly magnetic iron ore recently discovered in the human brain.

Eventually, they said, they hope their work will lead to a better understanding of the cause of epileptic seizures -- essentially electrical storms in the brain -- and improve treatment of the debilitating illness.

Some neurologists said that other research has already shown that magnetic fields can provoke seizures in some patients. But members of the U.S.-Swiss team said previous studies have not produced such clear-cut results.

Michael Fuller, a geophysicist with the University of California at Santa Barbara, said the magnetic fields studied so far are 100 times stronger than the Earth's, which makes compass needles jump. They are about the same strength as fields that form around operating hair dryers and other electrical appliances.

A magnetic field is the space around a magnet or electric current where the magnetic force is felt.

In recent years, investigators have published a number of studies on possible links between strong electrical and magnetic fields and several ailments, including cancer.

But in generating their magnetic fields, the epilepsy researchers used DC, or direct current, meaning that the electrical energy flows in only one direction. Most machinery and appliances operate on alternating current, in which the direction of the flow of energy switches rapidly back and forth.

Mr. Dobson explained that an alternating current would have interfered with the experiment's record ing device.

Patrick Brysse, a professor of environmental health at the Johns Hopkins School of Public Health, has studied the incidence of cancers in electrical workers. He said the distinction between AC and DC is important.

"There's nothing to suggest that DC current would behave like AC currents" in terms of its potential effect on living things, he said.

But he also said, "I think the findings are certainly interesting, and not inconsistent with a growing body of literature which suggests these fields may interact with biological systems in ways not thought previously possible."

John Paul Dobson, a geophysicist with the Swiss Federal Institute of Technology, said the researchers studied two patients with drug-resistant epilepsy at the University Hospital in Zurich. Electrodes were planted inside the skulls of both patients so that Dr. Heinz G. Wieser, a neurologist, could pinpoint that part of the brain where their seizures began and remove it.

The patients were fitted with a helmet made of a plastic bucket wrapped with wires and hooked up to an electrical source. When the electricity was switched on, the coils generated a weak magnetic field. Meanwhile, the scientists monitored brain wave activity with an electroencephalograph.

In both patients, monitors detected seizure patterns a few seconds after the magnetic field appeared.

Magnetism triggered seizures in the area of the hippocampus where the patient's natural seizures began.

TC As geophysicists, Mr. Dobson and Mr. Fuller are interested in the role magnetite might play in brain chemistry.

So far, biologists have found fragments of the mineral scattered seemingly at random through brain tissue. Mr. Fuller said researchers plan to look closely for smaller pieces of magnetite in the synapses, the gaps across which the brain's electro-chemical messages travel, or embedded in part of each neuron.

In the short run, Mr. Dobson said, the research might benefit epilepsy patients who have electrodes implanted in their heads. Now these patients might wait days or weeks for a seizure to occur so that surgeons can pinpoint its source.

If magnetic fields can reliably trigger seizures in affected areas of the brain with the flip of a switch, Mr. Dobson said, "it will save the patients some really difficult times."